Land grid array packages with solder bump interconnection, such as over-molded pad array carriers (OMPACs), are becoming increasingly popular. The use of flip chip bonding using solder bumps is also becoming widespread. In both of these technologies, the formation of solder bumps on the substrates or chips is a major concern.
Currently, for OMPAC type packages, solder balls are picked up with a suction plate and then attached by flux onto the substrate. The entire operation is carried out by a robot. As the pick-up and delivery of the balls is not completely repeatable, multiple passes consisting of inspection and re-deposition is required. Moreover, the robotic process is slow and is not conducive to low cost mass production.
Solder bumping of chips and wafers requires elaborate semiconductor fabrication facilities involving masking (photoresist or hard mask), evaporation or plating, as well as ancillary chemical operations. These facilities are highly capital-intensive.
Accordingly, it is highly desirable to have a low-cost method for forming interconnect bumps, such as solder bumps, on substrates that doesn't require the use of expensive robotic equipment and can be performed in a simple and reliable method.